[clang] Suppress octal literal diagnostics from system macros (PR #192481)

[Aaron Ballman via cfe-commits]

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@@ -166,5 +166,27 @@ void foo() {
 }
 #endif
 
+#172 "system_header.c" 3
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AaronBallman wrote:

I can change the extension, good call. It's the `3` in the GNU line marker that makes Clang think we're in a system header: https://gcc.gnu.org/onlinedocs/cpp/Preprocessor-Output.html

https://github.com/llvm/llvm-project/pull/192481